1. Field of the Invention
The present invention relates to design algorithms that are able to take into account a wide variety of nozzle-firing constraints in designing nozzle scheduling/firing algorithms that are specific for certain conditions. The algorithms may be realized as methods, incorporated into an appropriate apparatus (e.g., a computer, printer, etc.) or other device (e.g., an integrated circuit chip), or implemented as a program of instructions (e.g., software) embodied on a device-readable medium.
2. Description of the Related Art
An ink-jet printer renders images by ejecting tiny droplets of ink through nozzles carried on an ink-jet head onto an output medium. The print head and medium move relative to each other to sweep a two-dimensional area on which the image or other representation is rendered. Typically, the head contains multiple nozzles to minimize the amount of mechanical motion required to cover a two-dimensional area, while providing the desired printing resolution. Printing resolution is specified by a combination of spatial and color resolutions. Spatial resolution refers to the number of distinctly addressable drop locations on an output medium (e.g., a piece of paper). Color resolution refers to the ability of the printer to deposit multiple drops or multiply-sized drops at a given location on the medium.
An ink-jet head is characterized by a number of parameters, such as the number of nozzles, nozzle geometry, nozzle spacing, etc. Each nozzle can fire droplets at a certain rate determined by its construction, the actuation mechanism, the materials composing the head, and ink properties such as viscosity and surface tension.
The process of halftoning converts a continuous tone image to a representation that indicates the amount of ink to be deposited at each addressable location on the output medium. This information then needs to be translated to the actual firing of print head nozzles over space and time to render the desired image. The translation of the halftone processing result to nozzle-firing sequences is subject to constraints imposed by the desired spatial and color resolutions, print head parameters, ink and output medium. For example, the output resolution is typically higher than the spacing between nozzles (see FIG. 1), thus requiring multiple passes. The output medium may be composed of a variety of materials, such as, paper, cloth, plastic, etc., and the rate of ink absorption and the interaction between droplets on the medium is strongly dependent on the material properties of the ink and output medium. Further, due to mechanical misalignment and noise in the print head or medium transport mechanisms, printing all droplets along a given image row, in a single pass, may lead to undesirable visual artifacts. In other cases, if the nozzle firing rate for a given ink is too low to print at the required resolution for a given head speed, multiple passes of the head relative to the output medium, may be required.
While nozzle firing algorithms currently exist, the current technology does not provide a unified approach to automatically designing such algorithms to incorporate a variety of specifiable constraints in the form of design rules to achieve an appropriate firing algorithm for a particular printer/output medium.